Chemical element is a set of atoms which have an identical charge of a kernel and the number of protons coinciding with serial number in Mendeleyev's Table. The concept "element" was known from an extreme antiquity. But only the famous chemist Lavoisier in 1789 systematized chemical elements on types.
Instruction
1. Lavoisier carried to elements a number of simple substances – all metals and also phosphorus, sulfur, hydrogen, oxygen, nitrogen known by then. In addition, it carried light, a heatsort to elements and. "salt-forming earthy substances". Certainly, from a position of today, his many statements seem naive, but for those times it was the big step forward.
2. In the first half of the 10th century, efforts of Dalton and other famous scientists, accepted an atomic and molecular hypothesis of the structure of elements. She considers any chemical element as a separate type of atoms, and simple and complex substances as consisting, respectively, of atoms of one or different types.
3. Dalton possesses a priority in determination of atomic weight of an element as major indicator on which its chemical properties directly depend. Other famous chemist – Bertselius - did a great job by definition of atomic scales of elements. It in many respects promoted opening of the Periodic law by Mendeleyev. By this moment, 63 elements were known. By means of the Periodic law, became possible to predict physical and chemical properties yet not of open elements.
4. Subsequently fundamental works G. of Moseley and J. Chadwick thanks to which there was a modern understanding of chemical element as sets of the atoms possessing an identical positive charge of a kernel were published.
5. Strictly certain place is allocated to each element in Mendeleyev's Table. It has both the full name, and the reduced record form – the symbol consisting of one or two Latin letters taken from the Latin name of an element. For example, Fe (ferrum, iron), Cu (cuprum, copper), N (hydrogenium, hydrogen). Near a symbol of an element the following information on it is had: the serial number corresponding to quantity of protons in a kernel, the atomic mass, distribution of electrons on power levels, an electronic configuration.